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Metal-organic frameworks (MOFs) are superior ion adsorbents for selectively capturing toxic ions from water. Nevertheless, they have rarely been reported to have lithium selectivity over divalent cations due to the well-known flexibility of MOF framework and the similar physiochemical properties of Li+ and Mg2+. Herein, we report an ion-sieving adsorption approach to design sunlight-regenerable lithium adsorbents by subnanoporous MOFs for efficient lithium extraction. By integrating the ion-sieving agent of MOFs with light-responsive adsorption sites of polyspiropyran (PSP), the ion-sieving adsorption behaviors of PSP-MOFs with 6.0, 8.5, and 10.0 Å windows are inversely proportional to their pore size. The synthesized PSP-UiO-66 with a narrowest window size of 6.0 Å shows high LiCl adsorption capacity up to 10.17 mmol g−1 and good Li+ / Mg2+ selectivity of 5.8 to 29 in synthetic brines with Mg/Li ratio of 1 to 0.1. It could be quickly regenerated by sunlight irradiation in 6 min with excellent cycling performance of 99% after five cycles. This work sheds light on designing selective adsorbents using responsive subnanoporous materials for environmentally friendly and energy-efficient ion separation and purification. [ABSTRACT FROM AUTHOR]

1D nanochannels modified with responsive molecules are fabricated to replicate gating functionalities of biological ion channels, but gating effects are usually weak because small molecular gates cannot efficiently block the large channels in the closed states. Now, 3D metal–organic framework (MOF) sub‐nanochannels (SNCs) confined with azobenzene (AZO) molecules achieve efficient light‐gating functionalities. The 3D MOFSNCs consisting of a MOF UiO66 with ca. 9–12 Å cavities connected by ca. 6 Å triangular windows work as angstrom‐scale ion channels, while confined AZO within the MOF cavities function as light‐driven molecular gates to efficiently regulate the ion flux. The AZO‐MOFSNCs show good cyclic gating performance and high on–off ratios up to 17.8, an order of magnitude higher than ratios observed in conventional 1D AZO‐modified nanochannels (1.3–1.5). This work provides a strategy to develop highly efficient switchable ion channels based on 3D porous MOFs and small responsive molecules. [ABSTRACT FROM AUTHOR]

The novel oriented electrospun nanofiber membrane composed of MOFs and SPPESK has been synthesized for proton exchange membrane fuel cell operating at high temperature and anhydrous conditions. It is clear that the oriented nanofiber membrane displays the higher proton conductivity than that of the disordered nanofiber membrane or the membrane prepared by conventional solvent-casting method (without nanofibers). Nanofibers within the membranes are significantly oriented. The proton conductivity of the oriented nanofiber membrane can reach up to (8.2 ± 0.16) × 10-2 S cm-1 at 160°C under anhydrous condition for the highly orientation of nanofibers. Moreover, the oxidative stability and resistance of methanol permeability of the nanofibers membrane are obviously improved with an increase in orientation of nanofibers. The observed methanol permeability of 0.707 × 10-7 cm2 s-1 is about 6% of Nafion-115. Consequently, orientated nanofibers membrane is proved to be a promising material as the proton exchange membrane for potential application in direct methanol fuel cells. [ABSTRACT FROM AUTHOR]

Zeolitic imidazolate frameworks (ZIFs), a subclass of metal organic frameworks, are built of tetrahedral metal ions bridged by imidazolates. They have permanent porosity and relatively high thermal and chemical stability, which make them attractive candidates for many industrial applications. In recent years, significant progress has been made in developing ZIFs into membranes and thin films for gas separation, liquid separation (pervaporation) and functional devices. Various techniques, such as direct synthesis, secondary synthesis, reactive seeding and functional chemicals as linkers, and contra-diffusion synthesis, have been reported for the fabrication of ZIF membranes and films. As ZIFs have good compatibility with polymers, they have been incorporated into polymers with high loadings to form mixed matrix membranes. The resulting symmetric dense or asymmetric composite membranes exhibit good performance in gas separation and liquid separation via pervaporation. The recent developments of ZIF membranes/films, ZIF-polymer mixed matrix membranes and their applications are reviewed in this article. [ABSTRACT FROM AUTHOR]

The article offers information on use of ultrathin water-stable metal-organic framework membranes for ion separation. Topics discussed include exfoliation of two-dimensional (2D) monolayer aluminum tetra-(4-carboxyphenyl) porphyrin framework (termed Al-MOF) nanosheets; use of intrinsic nanopores of the Al-MOF nanosheets domain for ion/water separation; and long-term structural robustness in aqueous environment by exfoliated Al-MOF nanosheets.